/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.dx.rop.code;

import com.android.dx.rop.cst.CstString;

/**
 * A local variable item: either a name or a signature or both.
 */
public class LocalItem implements Comparable<LocalItem> {

	/** {@code null-ok;} local variable name */
	private final CstString name;

	/** {@code null-ok;} local variable signature */
	private final CstString signature;

	/**
	 * Make a new item. If both name and signature are null, null is returned.
	 * TODO: intern these
	 * 
	 * @param name
	 *            {@code null-ok;} local variable name
	 * @param signature
	 *            {@code null-ok;} local variable signature
	 * @return {@code non-null;} appropriate instance.
	 */
	public static LocalItem make(CstString name, CstString signature) {
		if (name == null && signature == null) {
			return null;
		}

		return new LocalItem(name, signature);
	}

	/**
	 * Constructs instance.
	 * 
	 * @param name
	 *            {@code null-ok;} local variable name
	 * @param signature
	 *            {@code null-ok;} local variable signature
	 */
	private LocalItem(CstString name, CstString signature) {
		this.name = name;
		this.signature = signature;
	}

	/** {@inheritDoc} */
	@Override
	public boolean equals(Object other) {
		if (!(other instanceof LocalItem)) {
			return false;
		}

		LocalItem local = (LocalItem) other;

		return 0 == compareTo(local);
	}

	/**
	 * Compares two strings like String.compareTo(), excepts treats a null as
	 * the least-possible string value.
	 * 
	 * @return negative integer, zero, or positive integer in accordance with
	 *         Comparable.compareTo()
	 */
	private static int compareHandlesNulls(CstString a, CstString b) {
		if (a == b) {
			return 0;
		} else if (a == null) {
			return -1;
		} else if (b == null) {
			return 1;
		} else {
			return a.compareTo(b);
		}
	}

	/** {@inheritDoc} */
	public int compareTo(LocalItem local) {
		int ret;

		ret = compareHandlesNulls(name, local.name);

		if (ret != 0) {
			return ret;
		}

		ret = compareHandlesNulls(signature, local.signature);

		return ret;
	}

	/** {@inheritDoc} */
	@Override
	public int hashCode() {
		return (name == null ? 0 : name.hashCode()) * 31
				+ (signature == null ? 0 : signature.hashCode());
	}

	/** {@inheritDoc} */
	@Override
	public String toString() {
		if (name != null && signature == null) {
			return name.toQuoted();
		} else if (name == null && signature == null) {
			return "";
		}

		return "[" + (name == null ? "" : name.toQuoted()) + "|"
				+ (signature == null ? "" : signature.toQuoted());
	}

	/**
	 * Gets name.
	 * 
	 * @return {@code null-ok;} name
	 */
	public CstString getName() {
		return name;
	}

	/**
	 * Gets signature.
	 * 
	 * @return {@code null-ok;} signature
	 */
	public CstString getSignature() {
		return signature;
	}
}
